1. Field of the invention
This invention relates to an image-forming apparatus such as an electrophotographic copier or printer, and particularly to technology for suppressing noise production while efficiently expelling water vapor emitted from a fixer to outside the machine.
2. Description of the Related Art
An example of an electrophotographic image-forming apparatus of related art is shown in FIG. 5. And, the vicinity of a fixer of this image-forming apparatus 900 is shown in FIG. 6. The image-forming apparatus 900 has a laser reading device 1 for directing a laser beam corresponding to an image signal at a photosensitive drum 2 and forming an electrostatic latent image corresponding to the image signal on the photosensitive drum 2, which is charged by a charger 3; a developing roller 4 for developing the electrostatic latent image; paper feed rollers 5 and 6 for feeding paper from a cassette tray 7 to the photosensitive drum 2; a transfer roller 8 for transferring a toner image developed on the surface of the photosensitive drum 2 to a sheet of paper by means of electrostatic force accompanying electric discharge; and a fixer 14 for fixing the image to the paper by applying pressure and heat with a pair of fixing rollers 12.
As shown in FIG. 6, paper ejected upward from the fixer 14 is guided to ejecting rollers 24 by paper guides 16 and a paper feed chute 20 and is ejected through a paper delivery opening 18 into a tray 22 formed in an upper face of a housing member 10. Because in the fixer 14 moisture contained in the paper with the toner image formed upon it is heated and becomes water vapor, air vents 26 for venting heat and water vapor from the fixer 14 are provided in the upper cover 10a around the fixer 14. Ribs 11 are provided pointing downward in positions adjacent to the air vents 26 on the rear side of the housing member 10.
As can be seen from FIG. 6, the route from the fixing rollers 12 to the ejecting rollers 24 is a section where the paper feed direction changes greatly over a short distance. Consequently, in this location, scraping noises caused by friction between the paper and the paper guides 16 or the paper feed chute 20 arise. Also, in this location, it sometimes happens that vibration of gears driving the fixer 14 and the ejecting rollers 24 is transmitted to the paper and gives rise to further noise. To avoid these noises leaking to outside the machine, the area of the air vents 26 around the fixer 14 is kept to within a certain range. And because of this, water vapor emitted from the fixer 14 is not rapidly vented through the air vents 26 and tends to stagnate. Consequently, the possibility has arisen of some of the water vapor condensing on the housing member 10 around the fixer 14 and eventually dripping onto the paper as it is transported. As a result, problems such as paper jamming and paper soiling and crinkling have arisen.